In 1805, Spain had made available its navy to Napoleon in order to deal in the naval war against the British, culminating in October with the destruction of the Spanish Navy in the naval battle of Trafalgar.

The Spanish fleet maintained trade with the colonies was seen, from that moment, very weak. Napoleon, unable to invade Britain, which had secured their dominion over the seas, decided a trade blockade against the United Kingdom by preventing the entry of their products to Europe.

But in 1807, the blockade was rejected by Portugal, traditional ally of England. Then the Emperor of France decided the invasion of Portugal.

France and Spain occupied Portugal at the end of 1807, the British crown ordered the English Admiral Sidney Smiththat rescue and relocate to the Portuguese royal family to his dominions in South America, being installed the Portuguese crown in Rio de Janeiro.

By February 1808, England planned defeating Viceroy Liniers and replace it with the Regent Princess Charlotte, daughter of King Carlos IV of Spain, establishing in Buenos Aires, an English protectorate, instead the Viceroyalty of the Río de la Plata.

On July 4, 1808 the King of England, George III, decreed the cessation of hostilities with Spain ended the blockade of Spanish ports and allowed the entry of Spanish vessels  to the ports of Great Britain The spain traditional adversary became ally and France, which had always been an ally of Spain, now becomes the enemy. The plans of the English protectorate in Buenos Aires vanished.


France aided by Spain; occupied Lisbon, capital of Portugal in November 1807. The English Admiralty warned of this Franco-Spanish advance, instructed Sir Sidney Smith to take command of a naval squadron that should lead to the royal family of Portugal to Brazil. He disembarked into the River Tajo, in early 1808, and moved  the Portuguese royal family, government and the leading members of Portuguese society installing the court to Brazil and the capital in Rio de Janeiro.

The events in Europe impacted on Spanish America and especially in the Viceroyalty of the Río de la Plata. News from Spain that brought the English ships anchored either at the port of Montevideo or Buenos Aires, were eagerly read and discussed by the local population. Were printed or reprinted sides and proclamations about European events. In February 1808 arrived in Buenos Aires the news of the arrival of the Portuguese Court to Brazil.

It began a campaign against the viceroy Liniers, led by Elio from Montevideo and Martin Álzaga from his seat in the Cabildo of Buenos Aires. The Cabildo of Buenos Aires sent a letter signed by Álzaga and other hearers to the Board of Sevilla requesting that relieve of command Viceroy Liniers, considered French

Princess Carlota Joaquina was the daughter of the King of Spain, Carlos IV, sister of Ferdinand VII and was married to the King of Portugal. As a descendant of the kings of Spain, aspired to the succession of the throne as far that his father and brother, (legitimate heirs) were prisoners of Napoleon. To do this she became acquainted with the admiral of the British fleet that had moved to the Portuguese royal family to Brazil, Sidney Smith, and together they devised a plan to establish a regency in the Río de la Plata. To do this they established contact with Manuel Belgrano and patriots like Castelli through the trader Felipe Contucci.

It was very important the intelligence work being done by the British Ministry of Foreign Affairs. Constantly receiving information provided by English traders and travelers who were in South America. So did the British officers, especially the Sailors.

There were several projects of Independence in Buenos Aires, which were known to both the English informants, the British Foreign Office, the governor of Montevideo, Javier Elio, and the Portuguese court in Rio de Janeiro. Consequently, the activity of the conspirators was being watched. While these independence efforts were not coordinated, due to the distance to which actors were: London, Rio de Janeiro, Buenos Aires, and were also difficult secret communications in which the Patriots had to act. Their lives were in danger if they were discovered.

An unexpected event for Spain and its colonies occurred on July 4, 1808 the King of England, George III, ordered the cessation of hostilities with Spain ended the blockade of Spanish ports and allowed the entry of Spanish ships to the ports of Great Britain. This modified across the political board of Europe and the colonies. Indeed, England, the traditional enemy of Spain became an ally and France, which had always been an ally of Spain, now becomes the enemy

It had been prepared a third invasion of Buenos Aires, more powerful than the previous two, 1806 and 1807, which did not took place Spain when turn into an ally of England, while its territory was occupied by imperial forces of Napoleon.